This is because Wagner has become the only composer around whom any ethical debate exists.
But he was by no means the only composer developing new modes of chamber music.
"I'm the only composer in the world who doesn't care if it's heard."
He was considered the only popular composer in the world who ruled a law-enforcement department at the same time.
Schoenberg was not the only composer to use this way of composing.
Presumably, that is, for he was the only composer represented here who took no active part.
Johnson is the only composer to receive this rarely given award twice.
But he wasn't the only composer to flirt with the notion.
He is the only composer to have three scores on the list.
Wagner is the only composer who ended up with his own -ism.